Overrunning decouplers for serpentine drives used on internal combustion engines are well known. They operate to reduce torsional vibrations in the serpentine drive caused by operation of the engine.
Decouplers typically include a one way clutch, which operates so the decoupler only transmits torque in one rotational direction. They also include an isolation spring which operates to dampen the torsional vibrations between the decoupler pulley and the accessory device driven by the pulley.
Decouplers are typically installed on the alternator or crankshaft of an internal combustion engine because the alternator has the highest inertial load of the accessories driven by the serpentine drive.
Use of an isolating decoupler involves advantages such as increasing the life of the serpentine belt and decreasing the spring force requirements of the belt tensioner for the serpentine system. It can also increase the operating life of the alternator.
Representative of the art is U.S. Pat. No. 8,006,819 which discloses an overrunning accessory decoupler with a locking mechanism which provides the desired overrunning accessory decoupler functionality and also permits torque to be transferred from the accessory to which the decoupler is installed to the drive of the engine when desired. In one embodiment, the decoupler includes a locking mechanism that is controlled by centrifugal forces developed in the decoupler to lock the decoupler to permit the accessory to transfer torque to the drive to start or boost the engine.
What is needed is an isolator decoupler comprising a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid. The present invention meets this need.